On (q + t, t)-Arcs of Type (0, 2, t)

In this paper we construct an infinite series of (q + t, t)-arcs of type (0, 2, t). We show that this construction includes the Korchmáros-Mazzocca arcs, and we gain new infinite series of examples, too.     

CD Spectroscopic Study of Absolute Conformation and Configuration of Some 4-Hydroxychromans

CD data of the optically active 4-hydroxy (1–5) and 4-acetoxy chromans (6–8) were analyzed by two different approaches. The Snatzke-Antus treatment of chiraly perturbed chromane chromophore revealed M absolute conformation and 4S absolute configuration of the alcohols, i.e. P absolute conformation and 4R absolute configuration of the acetates. The proposed absolute configuration of the optically active alcohols was confirmed for 1 and 2 by the chiral excitone coupling method applied on their benzoates 9 and 10.     

On Sets without Tangents in Galois Planes of Even Order

We show that the cardinality of a nonempty set of points without tangents in the desarguesian projective plane PG(2, q), q even, is at least q + 1 + $ \sqrt {q/6} $ provided that the set is not of even type.     

Proof of a conjecture of Metsch

In this paper we prove a conjecture of Metsch about the maximum number of lines intersecting a pointset in PG(2,q), presented at the conference “Combinatorics 2002”. As a consequence, we give a short proof of the famous Jamison, Brouwer and Schrijver bound on the size of the smallest affine blocking set in AG(2,q).     

Characterisation of Specific Activities and Hydrolytic Properties of Cell-Wall-Degrading Enzymes Produced by Trichoderma reesei Rut C30 on Different Carbon Sources

Conversion of lignocellulosic substrates is limited by several factors, in terms of both the enzymes and the substrates. Better understanding of the hydrolysis mechanisms and the factors determining their performance is crucial for commercial lignocelluloses-based processes. Enzymes produced on various carbon sources (Solka Floc 200, lactose and steam-pre-treated corn stover) by Trichoderma reesei Rut C30 were characterised by their enzyme profile and hydrolytic performance. The results showed that there was a clear correlation between the secreted amount of xylanase and mannanase enzymes and that their production was induced by the presence of xylan in the carbon source. Co-secretion of α-arabinosidase and α-galactosidase was also observed. Secretion of β-glucosidase was found to be clearly dependent on the composition of the carbon source, and in the case of lactose, 2-fold higher specific activity was observed compared to Solka Floc and steam-pre-treated corn stover. Hydrolysis experiments showed a clear connection between glucan and xylan conversion and highlighted the importance of β-glucosidase and xylanase activities. When hydrolysis was performed using additional purified β-glucosidase and xylanase, the addition of β-glucosidase was found to significantly improve both the xylan and glucan conversion.     

Enantioselective Synthesis of α-Alkoxy-Phosphonates by Chiral Phase Transfer Catalysis

Abstract

Enantioselective PTC phosphorylation of aldehydes performed in a two phase (aq. NaOH/toluene) system mediated by chiral crown ether incorporating one or two sugar units. To avoid the rearrangement of hydroxy phosphonate 3 to nonchiral mixed phosphate ester 4 the hydroxy phosphonate was trapped by alkylation to give 5.     

New Synthesis of Substituted Cyclopropanephosphonic Acid Esters

Abstract

Aminocyclopropane phosphonic acids are considered to be “transition state analogues” of aminocyclopropanecarboxylic acids and they may serve as enzyme inhibitors¹. We attempted to synthesise aminocyclopropane derivatives by a new route². Phosphonoacetic acid allylic esters were subjected to an intramolecular, radical cyclisation in the presence of iodine, solid potassium carbonate and phase transfer catalyst.     

The first enantioselective synthesis of α-aminophosphinates

The first enantioselective synthesis of substituted α-aminophosphinic acids was carried out by the addition of ethyl phenylphosphinate to chiral imines in the absence of base or other catalyst.